This subproject is one of many research subprojects utilizing the resources provided by a Center grant funded by NIH/NCRR. The subproject and investigator (PI) may have received primary funding from another NIH source, and thus could be represented in other CRISP entries. The institution listed is for the Center, which is not necessarily the institution for the investigator. The objective of project was to characterize the aging behavioral phenotype in the rhesus monkey and determine which neural changes are correlated with specific behavioral declines. An initial phase of the study involved the collection of baseline health data, including ophthalmic examinations and magnetic resonance images of the brain, to ensure that the monkeys are not diseased so that any behavioral deficits that may be identified are attributable to normal cognitive decline. The application of well-characterized behavioral tasks taps specific cognitive domains, including visual recognition memory, spatial working memory, and executive function. We successfully identified changes in cognition that are typical of aging as well as changes in the brain that accompany behavioral decline. A key overall finding of this study was that some aged monkeys appear to be spared from serious cognitive losses, while others are markedly impaired. Our current approach to investigation of these different patterns is to focus on middle age, when changes are just beginning to occur. This characterization of which monkeys are likely to progress to worsened cognition and which are likely to remain unimpaired will assist us in delineating optimal strategies for mid-life interventions.